Im trying to read an elevation on a plat of survey but they just give these numbers 647 and some like that. How do I read them

I can only assume that 647 is elevation in ft. MSL - Mean Sea Level. Where are you located? Is 647 ft. appropriate for your area.

Hi ma0641, Im located in Illinois, and what I really meant was that those numbers are for contour lines on a plat of survey, you know like different lines with different numbers like 647. I know they are different elevations but how do I convert them to inches if Im doing a 3d drawing with all its elevations. Thanks

If it is feet, X 12 = inches. If you are building a house, you would use a transit. The problem with a plat is that the base is planar but the elevations are not. Typically you would find a set point at the elevation, mark it as 0 and then use the transit for up and down.