There is no option given for changing the clothes/outfits of the Player in the GTA 3 definitive edition, which means, you can’t change the clothes of the player in the GTA 3 game.
It may be possible through mods, but very less mods are available on some websites. Also, that particular mod has a very low chance of working.
So, in simple words, you can’t change the cloth of a player in GTA 3, if you really want to change and want to play with fun, then you can play GTA vice city, GTA 4, GTA 5, GTA San Andreas game. In these games, you can change everything which is available for change but in GTA 3, no particular option is available for changing clothes or outfits.