There is a complete procedure on doing this in the NTP. Here's a quick overview.
1. Do a tempkate audit by running LD 1
2. Remove FFC AREM in LD 57
3. LD 43 do an EDD
4. LD 43 do a BKO
5. LD 143 type upgrade, utilities,archive database,enter name for archive,enter 1 to list customer database, it will list archives available and it will archive to CF.
This procedure will work for 6.0 thru 7.5 and this pricedure will convert your small system TN's to a Large TN format. There is also an NTP that shows you how the database will convert as far as loops etc. Fpr example Card 1 will be converted to 0 0 1, Card 11 will be converted to 0 1 11 and so on. Find the procedure, read it thoroughly and make notes.