Agreeing with JimS123, depending on the boat mfgr and model, with the engine (motor) sitting on the transom (the vertical board at the rear of the boat upon which the engine sits), with the clamp brackets tightened and all, Set the boat level.
Then lift the engine lower unit up and look under the engine at the bracket that clamps to the outside of the transom. Your engine may have a "Transom Lock" lever, up front (if a tiller model), just above the transom top which you will have to press to get the lower unit to to up.....usually if you shift into Forward gear, the lever is automatically released and you can lift leg of the engine easily................. There will be a stainless steel pin (⅜" or thereabouts) that stretches across the bracket and you will find several sets of holes in the brackets for adjusting the location of that pin/bar up or down. The holes you select sets the angle of the engine to the angle of the boat.
Select a set of holes, insert and lock the pin and let the lower unit leg of the engine down on the pin. Go to the side of your boat and see if the engine is vertical to the "level" hull (90 degrees). If not, move the pin up or down till you get it vertical.
Then take a straight edge, yardstick works fine, and project it straight out the back, flat against the bottom center of the hull, and continue it out till it passes the lower unit. Look at the location of the horizontal plate (antiventilation plate located just above the propeller blade tips) vs your straight edge.
If you have the right engine length for your boat, the AV plate will be roughly within +/- 1" of your straight edge. If it's 5 inches off either direction, the transom and the engine length are not compatible....like a 20 inch transom with a 15" engine skeg, or vise versa.
Assuming you are within the inch (more or less) if the plate is lower than the straight edge, the engine will do better getting your boat going (up on plane making your speed increase drastically) if you are tiller steering (at the rear....stern...of the boat), and for your listed combination, that's where I would want mine. Having it even or slightly higher is really for higher speed, higher HP boats designed for high performance. You shouldn't need, nor want a "Jack Plate"......again, something for the Jet Set.
Good luck.