i want to reset my ipad with manual mode,but it says firmware is not compatible

Actually, no it does not. What do you mean by "manual mode"?

If trying to do a full reset to the original new, out-of-the-box state there are two ways to do that.

One is to go into settings and under General, run the "Erase All Content and Settings" - once that is run, you will be back to the original iOS setup screen.

Two it to plug it into iTunes on your computer and restore it to new - again at the end of which you will be back to the setup screen.

If you have jailbroken your iPad, then nobody here can really help you with that, and you may encounter problems with restoring back to a non-hacked iOS state, even finding it is impossible to do.