well, this information you can find in the catalogue IK PI. The amount of DP Slave data for the CP 342-5 is

240 Byte Input and
240 Byte Output.

To get the Slave in the 3rd party Master system you will need the GSD File for the CP which you can find in the following Download:

PROFIBUS GSD files : SIMATIC

Best regards

I am sorry, but I can not help you to configure your 3rd party DP Master. But I can try to explain. PROFIBUS DP is based upon a modular system. To transmit data you need modules that are configured to transfer Data. So what you have to do to get 240 Byte Inputs and Outputs you have to configure several Modules, depending how much Data your Master is able to transmit.

The CP 342-5 is able to have up to 64 Byte or 64 Words consistent Data in one Module. So you would have to configure up to 4 Modules (2 x 64 Words input and 2 x 64 Word output) for the Slave.
How you configure this in your Master is not known by me, I am sorry. To get this you may have to contact the manufacturer of the DP Master you use.

Best regards