You can try "upsampling." This will increase the resolution of the original pictures by adding more pixels - software guesses where they should be. However, note that you may not be thrilled with the results. Upsampling can work to a degree but too much upsampling will degrade the quality of the picture anyway, defeating the purpose.
I'm not sure you can upsample with Paint - I doubt it. I use a free image editing program called GIMP. It's a very powerful program, though unfortunately it's also a bit complex to learn. There are a lot of tutorials online, but it may still take you a long time to figure out. If you can use some free version of Photoshop or Paint Shop Pro on a Windows PC, that might work for you too. I wouldn't be surprised if there are websites that will upsmple for you automatically - it's a fairly easy thing to do.
You might simply try printing a few of your questionable phone pictures before making a book and see how they look without any upsampling. Print at about the same size they would be printed in the book. (8x10?). FYI, photo websites that sell prints will automatically resample your images before printing and may upsample automatically. Shutterfly probably does the same thing when they make their books. If the prints you make look OK, then try the book.
If you want to print out pictures or make books in the future, I suggest you buy a real camera. Phone cameras, even with higher resolution, usually can't deliver the quality of a real camera. Yes, some of the expensive phones like iPhones, Pixels, and Samsung phones may have great phone cameras but you'll still get better quality with a good camera.
