FireRed cannot complete the Pokédex alone. You need LeafGreen for Sandshrew, Vulpix, Slowpoke, and Starmie. You need Colosseum (GameCube) for Suicune. You need the (an event item no longer distributed) to access Deoxys.
Several reputable community sites host these files for various regions (USA, Europe, Japan): pokemon fire red 100 save
A "100% complete" save file for typically includes more than just finishing the main story. Based on community standards from platforms like Project Pokémon and GameFAQs , here is the text description of what such a save usually contains: Pokedex & Team FireRed cannot complete the Pokédex alone
: Own all 150 Kanto Pokémon (Mew is excluded). You need the (an event item no longer
100% Save File Pokémon FireRed is a pre-completed game file that allows you to skip the grind and jump straight into endgame content with a full Pokédex and powerful items. What’s Typically Included in a 100% Save Complete Pokédex