My 4010 john deere the clutch feels like it's slipping. I've heard I just need to adjust the pedal but I'm not sure how. Any Help?

Crigby will be here later with more specific instructions but then general clutch/brake adjustment is similar on most all tractors. The pedal operates a rod that atticukates with a linkage that moves a pulley to tighten the tension on the drive belt. Have someone operate the clutch while your observe the rods moving, hold a flashlight on the rods, you will see on rod is threaded and can be disconnected, tighteneed or losened and reinstalled, usually tightening is what you want. If you over tighten you will have too much tension and the brake will likely not fully disengage.

Hi,
Since you have a clutch, I will assume you speak of that early 1960s monster with the six cylinder engine. There is a newer CUT, but it is a hydro.
You can get a pdf format parts manual from Deere at:
John Deere - Parts Catalog
And typing in 4010. Then pick the one with the red pdf symbol. Page 30-4 (60) will show the linkage and item #3 is the addjustment. By loosening the pinch bolt, you will be able to move the pedal/relieve pressure from the linkage. Any other slippage and I am afraid you have a major teardown on your hands.
Peace,
Clarke
PS It is a large file, but it is free.