You'll need to do this in steps, and for that, I think you'll need to use
VB or VBA. Essentially, you want to read the first row from the header table and write it to the second header table, then immediately reread the second table to get the new record's primary key (assuming it's an AutoNumber field). Once you have the new primary key, you need to process all of the detail records for the original header record. For each one, change the foreign key field to the value of the new header record's primary key, then insert the detail record into the second detail table. Your code might look something like this pseudo code:
Get all Header1 records
Do While Not Header1.EOF
Write the current record to the Header2 table
Get the highest primary key on the Header2 table and save
Get all Detail1a records for the current Header1 record
Do While Not Detail1a.EOF
Write record to Detail2a with new foreign (primary) key
Loop
Get all Detail1b records for the current Header1 record
Do While Not Detail1b.EOF
Write record to Detail1b with new foreign (primary) key
Loop
.
etc.
.
Loop
Hope this helps.
Pete