Make posts from 500 id to 3000 ??

Hello everyone!

how to make so that wordpress saves posts statring from 500 id and last would be 3000 and when 3000 is reached it rewrites new post (3001) to 500 id ???

And one more thing: in my BD post starts from 71** count (the last id is 7145) but ther’s only 400 posts and ii wonder how to force wordpress to write new post in not existing ID (or how to change all ID’s starting from 1) ??