You can connect a 4 wire RTD to a 3 wire instrument. Just use 3 of the wires. Generally a (4) wire RTD will have 2 white wires and 2 red wires. The active element is between a red and a white wire. The remainig wires are for lead wire resistance compensation.
Red -------------|VVVVVVVVVVV|------------------------White
Red________|