You'd need a 3000×2400 image, which is 7.2MP. The calculation is quite simple. DPI means dots per INCH. You want a print 10 INCHes wide, so for 300 dots per inch, you need 300×10 dots, or 3000.
So you can "up-size" (interpolate) to get your 300dpi, or you can leave the images alone and print with what you have. A 3mpxl image will normally make a very decent 8X10. If you need to print larger, a 5 MPXL image will work well, up to, double that size (16X20).
