I have a polaris ranger 6x6 500cc the plug in it now is a ngk bkr5e 7938. a friend gave me 2 unused ngk b7e s plugs and said that they wood run fine. Are these 2 ngk b7e s ok or what?

The figure 7 represents the heat range of the plug. Usually it is unwise to deviate from specifications unless problems force choosing a different heat range. If the spark plug regularly fouls then a hotter spark plug could improve the problem - with NGK that would mean moving from 5 to 4.

Any move must be made with care to avoid the engine damage possible if the spark plug is too hot.

Hot and cold plugs, incidentally, indicate the amount of heat the spark plug dissipates from the centre to the body and doesn't affect the temperature of the engine. Broadly cool running engines need hot spark plugs and hot running engines need cold plugs so in each case the spark plug nose will achieve the self-cleaning temperature without becoming too heated.

Moving from a 5 heat range to a 7 (NGK) is moving to a colder plug so yes it will run fine, at least for a while, though you could find plug fouling might be a problem...