Change IMEI on prepaid data SIM

Hi,

I need to activate a couple of Sierra Wireless USB modems that need to be used as a backup data connection for a network router.

I could not find the software/drivers to make this modem work with a Mac running High Sierra 10.13.6  I activated the SIM in an iPad. Now I need to change the IMEI number that has been assigned to this SIM to the one for this modem.

Please note that this is a pre-paid plan!

Looking forward to your advice,

Rogier