1. If WC is not dismantled yet and is not sealed with silicone at the back.
Insert a thin long object (eg: long ruler) into the gap between the WC and the wall, and run it down to the ground (as per direction marked in red). If there is no obstruction, then it is S trap (discharge hole on the floor).
2. If WC is not dismantled yet and is sealed with silicone at the back.
Your current WC is fully flushed to the wall, so we are unable to determine the trap type.
For accuracy, you may wish to dismantle the WC to confirm the trap type and trap distance prior making purchase.