According to wikipedia (and Entertainment Weekly) it says "Hallelujah Church of Scranton".
''We got the van at a used car lot,'' Pam told us. ''We think it says
'Alleluia Church of Scranton' in Korean.''' I'm going to leave it to
one of you Korean-reading Dunderheads to verify this, but given how
the rest of the episode played out, let's assume that's accurate.
The sun was coming up, and Pam wondered if Michael by any chance
brought coffee along for their delivery voyage. ''Milk and sugar,'' he
said, and handed her a gigantic travel mug. She took one sip and made
a disgusted face. ''Is this just milk and sugar?'' I think the best
part of this whole exchange was Ryan's strangely intense stare.
Ryan, Pam, and Michael were unloading boxes in a client's parking lot
— do most businesses get paper delivered so early in the morning? Can
they not accept deliveries during the day? Hmmm... — when a Korean
woman headed for the van. ''It's not for the church!'' Pam shouts.
''It's a paper company now.'' Pam knows how ridiculous she sounds, but
in another stand-out episode for Jenna Fischer, she's also trying to
keep it together.
Google Translate seems to concur
스크랜튼 의 ' 할렐루야 교회