Can anybody point me in the right direction to help me get higher resolutions on my two Mint 18.2 MATE 64-bit desktop machines?

One is running an AMD HD3850 1GB video card, the other is running the on-board Intel GMA 3100 card.
Linux drivers are a mystery to me...can anybody tell me where I can go to find drivers to let me use these cards at HD1080p resolutions? I know they are both technically capable of HD display resolutions, but the maximum the Display Properties window is letting me select when hooked up to my Sony 28" HDTV is 1360x768?
Cheers for any help and suggestions!