IF the question is asking for the first Biblical manuscript that used "satan" as a name, then the answer must be that there is none. The Hebrew word "satan" is not a name. It is properly a noun that is sometimes used as an adjective, and it is properly translated in Young's Literal Translation as "adversary." (See Strong's Heb. 7854 - Biblehub)
Anyone who stands against, or opposes another is an adversary (satan) to the other as the messenger of YHVH (Yeshua) was to Balaam in Num. 22:22, 32.
and the anger of God burneth because he is going, and a messenger of Jehovah stationeth himself in the way for an adversary to him, and he is riding on his ass, and two of his servants [are] with him, (Num. 22:22, YLT)
and the messenger of Jehovah saith unto him, `Wherefore hast thou smitten thine ass these three times? lo, I -- I have come out for an adversary, for [thy] way hath been perverse before me, (Num. 22:32, YLT)
Anyone who stands against YHVH, or Yah's people is an adversary, and these are most often human men and women who reject or scorn or despise Yah's word. Most often the context of the word "satan" in the Hebrew scriptures is applied to earth-born men (Lev. 18:18; Num. 10:9; 1 Samn. 29:4; 2 Sam. 19:23; 1 Kings 11:14; Esther 3:10; etc). But, sometimes God calls Himself an adversary to the people (Jer. 10:18).
The context of the use of "adversary" in 1 Chron. 21:1 is again of God standing against the people. The article used in 1 Chron. 21:1 is not "the" but "an", so an adversary stood up against Israel. The commentaries are somewhat mixed on this verse, but most attribute it to God's wrath against Israel finding the parallel from 2 Sam. 24:1 -
And the anger of Jehovah addeth to burn against Israel, and [an adversary] moveth David about them, saying, `Go, number Israel and Judah.' (YLT)
So, again God called Himself an adversary against Israel because of their sins. It is mankind who is in an adversarial relationship with YHVH, and that is why we needed our mediator and savior Yeshua / Jesus.
The word "satan" began to be used as a name for the belief in an evil spiritual entity some time in the 2nd century AD (CE) because of a misinterpretation or misunderstanding whose origin derived from pagan beliefs in a Persian two-god system of a "good" god and an "evil" god. This false pagan belief was so universally accepted that men began applying it to the scriptures.
So, the early church "fathers" read their biases and false beliefs into their writings and expositions of their interpretations of scripture. It is often cited that Jerome mistranslated the Hebrew word "helel" from Isa. 14:12 into the Latin Vulgate as "Lucifer" which was an error, and it began to be used in the Latin speaking regions as a name for "Satan". (See my post on Slandering Angels here).
It is not certain when the word "satan" began to be capitalized and used as a name, but it is entirely due to human error that this concept is so embedded in people's minds. It comes solely from false teaching which the article here points out.
There is no spiritual being named "satan" in the scriptures. There is no such thing as "Lucifer." The adversary of Job, and of Luke 22:31 is given capitalization through custom and habit assuming the definite article "the" indicates an evil spiritual being. But in both cases this "adversary" is subject to God's will, and seeks God's permission before he can act. This adversary then is under God's command, so ultimately God is the source of this adversary's actions, and cannot be presumed to be a devil or demon.
Further discussion here is too long for this site, and it is going to take a long time to help people unwind all of the history of the human errors of interpretation regarding the use of "Satan" and "Lucifer" as names of an evil spiritual entity.
Please see the following posts:
Testing the Spirits - Slandering Angles IVa
Testing the Spirits - Slandering Angels IVb
Testing the Spirits - Demons, Devils, & Idols VIa
Testing the Spirits - Demons, Devils, & Idols VIb
Testing the Spirits - Demons, Devils, & Idols VIc