Hello there i recently purchased some optex -70 sensors from yourself for replacement of the obsolete optex 100 plus ones.
On going to install them I found that the old ones have more wires eight as the new 70 ones only have six. So I was looking to see if there is a way to convert the old ones to the new

Based on the information you provided.  It appears that you have replaced the TF model with a TN model.  The TN model does not have DQ ( environmental disqualification, this can be used as a pre alarm or a shunt for the alarm to prevent false alarms)   so  in theory you can install the  beams without it.  It is also worth noting that the TF range has options for NO and NC contacts that the TN only has the options for NC.

Hello can you please confirm if you do a version the same as the 100 tf model instead of the tn models I have purchased please

You can use the AX-100TF

https://www.securitywarehouse.co.uk/catalog/cctv-c-1/detection-c-1_24/optex-4-channel-synchro-twin-30m-active-beam-nonc-relay-p-3367.html