How do I change out a 2 panel folding door to a basic nonfolding door?

I’d first get your measurements. Measure the inside frame top to bottom, side to side. Then I’d check home stores or search online to see if this is a common door size. If it is you’ll be able to replace it yourself, but if not it could be a bit more tricky. The bifold door is just on a track at the top and sometimes the bottom that once removed is just an open finished casing. There’s still the need for a door frame. This frame stops the door from swinging in and out like a saloon door. Look at other doors in your place to see what I’m talking about. Then head to your home center and see what’s available. Take pictures of what you have now and also have measurements handy. If it’s all too much then most of these home stores have installers that’ll come out and install it for you for a respectable fee.

What size is your opening? I think you are referring to bi-fold doors that are hung on a track. You will take the doors down and remove the track. You can buy a pre-hung door with the frame to install unless you have an odd sized opening. Basically, you insert the frame and nail it in place. If the opening is an odd size, you will have to purchase the door and build the frame. Study your other traditional doors to see how they are hung. You will need a miter saw to cut the trim around the door. You will probably need to put wood on the sides and overhead to frame out the opening. If you don't want to cut the trim with a miter saw, you can put square medallions in the corners and that will allow for a straight cut.

Check the dimensions of the folding door. They are normally shorter than a regular door (80"). You may need to do some framing to install the new door. It may be possible to use your existing frame and shorten the new door. Look at other doors in the house to see how they are installed.

Measure the opening then buy a door the same size you should be able to use same hinges