Usually I would like to see a picture of what is above the wall.
If there are only joists and no attic storage and no plaster ceilings and no point loads ,you might go with a 2x10 beam or header. You can bury it in the attic by keeping it flush with the bottom of the joists with joist hangers ,or keep it down into the room for a cased or trimmed opening.
You need to make sure your king and jack studs are carrying the weight down to the beam below the floor joists underneath. This is called the load path. If you don;t your new beam may be being held up with plywood and this is going to settle.
If you don't understand post back.
This sound easy to figure out but without seeing it you just don't know.