my rdr2 isnt working, i had recently bought a physical copy at the flea market of this game and i just now realized its a 2 part. (pls read body text)

The one i have currently is the one that says ‘disk 2’ and everytime i install it in my xbox it says “insert the first disk”(the first disk is to download the actual game) so i look online for the first disk and i for some reason cant find it, can someone help me out?