Adjusting infinity focus on Tamron A2 28mmF/2.5 - 02B

[shadows]

This lens has spent a lot of time on my camera since I bought it. But I was mainly using it for shooting subjects that were 3 meters away or closer.
So now I would like to shoot at infinity but right now infinity is reached just after the 3 meter mark then goes beyond infinity, which was a bit annoying when I tried to do some night shots (which is when I found out it went beyond infinity ) and focusing really became a pain to do.

I can see 3 small screws on the outside. So i'm guessing it is one of those or all 3 that I have to play with. But I'd rather ask first, just so I don't screw it up.