Where can i found the value of a miscut card. In my case i got 3 Earl of squirrel form unstable promo card that are well really off center.

Miscuts are complicated. Some people don't want them, some people want them more. It is really up to the buyer what they value.

That said, being silver-bordered may help you.

Old misprints are collectible. Misprints/miscuts on newer cards are getting too commonplace and may soon make the cards printed how they should be the rarer version.