It depends on what you want to say with "go back up"
Do you mean simply that it works again?
You mean fix the obvious security problems?
You mean make sure it never happens again?
Depending on what you want, either eliminating hacking or completely rebuilding the site, prices can range from cheap to very expensive.
Since it was hacked, completely rebuild the site from scratch. MAKE SURE THERE ARE NO SAFETY HOLES, it is the best way to do it.
If you are using Turdpress or some other similar garbage heap, all you can do is put a bandaid in the hack and WAIT FOR IT TO NEVER KICK YOU. It is IMPOSSIBLE to make a hack-proof Turdpress site.