1. Save your game
2. Go to Windows Explorer
3. Head to "Documents/Rockstar Games/GTA San Andreas Definitive Edition/Profiles/"user number"/
(For Gta III enter the "GTA III Definitive Edition" folder and for Vice City the "Vice City Definitive Edition" folder)

It should look like this:

4. Open up this website: https://gtasnp.com/upload
5. Drag and Drop in your save file ("GTAVSsf1.sav")

6. Click on Collectible Map
You can now see what you have missed.
Every Item that you have collected or every Stunt Jump that you have completed will not be shown on the map.

To refresh the map you have to save your game again and repeat the steps above.