You may have noticed that there is a rod running over the cap. You may have to struggle with that to get the bolts out and cap off.
I recall a spring is between the cap and the filter screen pressing the screen into the tractor so be a little careful when taking the last few treads of the bolts loose.
take a picture of the way it looks before you take anything else out so you know what it looks like when you put it back in.
Then the screen will be right there and is about .75 inch diameter. You can grab the screen with needle nose pliers and pull it out (try not to bend the ring of steel when pulling).
The screen is about 4 to 6 inches long to pull out of the tractor and that rod may be a little in the way but try not to bend the screen while getting it out.
clean the screen and then put it back together. Make sure the screen has been pushed back into the tractor so that it looks like it did when you took it apart.