The stock Quest M3 doesn't come equipped to accommodate thermocouples. If you want to add thermocouples, you have to find and install proper fittings for them.
The Quest comes with an analog thermometer positioned to monitor BT under the tryer. The analog thermometer fitting won't work for an 1/8" thermocouple. There's a threaded hole for an ET probe on the other side of the drum, but it's closed with a hex bolt.
At one time our member erics offered thermocouples and fittings for installing a 1/16" MET thermocouple, a 1/16" BT thermocouple near the sight glass and/or a 1/8" thermocouple at either the stock ET or BT positions. Unfortunately, eric no longer offers these products.This document details what erics offered
He also provides part numbers for thermocouples you can order. In a supplement near end, he provides part numbers and instructions for ordering and drilling your own DIY fittings to do substantially the same thing. The nice custom fitting for 1/8" probes that he used to offer can't be duplicated, but it can be replaced with a vented screw that need to be drilled slightly larger to accommodate an 1/8" probes. The 1/16" probe fittings he used to offer were the same as detaiied in the DIY section. The thermocouples can be ordered from Omega or other suppliers.
FWIW, my used Quest M3 came with original erics fittings and probes for a 1/16" MET probe, a 1/16" BT probe near the sight glass, and a 1/8" probe for ET and the stock analog thermometer for BT. I ordered some vented screws of both sizes and drilled them so I could replace the analog thermometer with a fourth thermocouple, and so I could thread a bare thermocouple into the bean chute to monitor exhaust temperature.
If you go the DIY route, be sure to order the drill bits eric specifies and use a drill press if you can.