If the optional A/D converter card is fitted then you can use a single ADAT cable to connect from either of the Octopre ADAT outputs to the ADAT in of the 002. Make sure that the bit depth and sample frequency are set to the same both in Pro Tools (or any other DAW you may be using) and on the front of the Octopre (note you can only choose 44.1 or 48KHz when using 8-channel ADAT Lightpipe). Also ensure that the clock source for the 002 is set to ADAT.
If the optional converter card is not fitted then you will need a 25-pin snake with balanced 1/4" jack connectors. Connect this to the line out connector of the Octopre and conect the jacks to input 1-8 of the 002. For channels 5-8, ensure that the nominal input level switches on the 002 are all set to +4.