virus in header.php

wp-content\themes\Innovate\header.php

Replace this file with a clean copy, to start, but there is no guarantee that that is the only place you have a problem. You should probably work through the “I’ve been Hacked” codex page.

No. As per my previous past, you don’t know if this is the only problem. Replace that file with a clean copy and work through the codex page I linked to.

It is base64 encoded. You can find decoders online but I can’t get it to decode to anything unreadable, but you don’t need to decode it. You need to get rid of it. You’ve been hacked. If you don’t have a backup, you need to replace all fo the files you can– IE the WordPress ones that you can re-download– and you need to check every single file on your server that you can’t replace. See this thread.

You were hacked once. If you don’t figure out how you were hacked and fix the problem you will be hacked again. You aren’t finished here.

Did you check directory file permissions?
Did you check the database for hidden admin users?

I’ve given you a couple of links with good information in them. Read those links (and follow esmi’s links when you find them), and do everything they say. If you want to know the answer to the question “Have I done enough?” then ask yourself “Have I done everything in those links?”. If you haven’t, you have not done enough.