Write MQTT tag values to PLC Tags

I'm trying to loop through MQTT Tags and write their values to PLC tags. Is there a way to do this through scripting?

Yes. Use system.tag.browse to browse and grab your MQTT tags needed using wildcards to filter out the tags you don't want. Grabbing the tag paths to be used with system.tag.readBlocking to grab the value. You will probably need to do some string manipulation to hopefully match your PLC tag names. Hopefully your tag names are identical minus the tag provider part of the path.
system.tag.browse - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)
system.tag.readBlocking - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)

You will need to take the above and build a list of tag paths and values in a list.

Then use system.tag.writeBlocking to take those tag paths and values and write them to your PLC tags.
system.tag.writeBlocking - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)
Use system.opc.writeValues to bypass the tag database and write directly to the PLC.
system.opc.writeValues - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)

The above will do it automatically - you can build the lists manually if only needing to do a few tags and not use system.tag.browse.