How can I delete spam from blog and reset next blogid?

[user 1-2-3]

One of my vBulletin installation was attacked by spam bots. I didn't find in Control Panel where can I mass-delete spam from blog, same I can make with threads.

Another question is how to reset nrxt blogid? I have 10 blogs and 1000 spam above them, so I want next ID to be 11, but not 1011.

Please, help to resolve this issue.