The inclusion of "-2021-" in your search likely refers to the date of the trainer release or a repack of the game. In 2021, interest in the game spiked due to the Definitive Edition release, leading many modders and cheat sites to update their tools. However, this can be misleading. If you are playing the original game, you need a trainer compatible with the original executable, regardless of the year the trainer was uploaded.
Right-click the trainer and select "Run as Administrator" to ensure it can inject code into the game. Download Trainer Mafia 2 1.0.0.1 -2021-
Eliminates the need to find or manage ammunition. The inclusion of "-2021-" in your search likely