How do I fix this error? It says "warning: invalid conversion from 'long int*' to 'long int' [-fpermissive]
This is most likely not what you want to be doing

//declaring variables of functions
FM = FindMax(new long);
FA = FindAvg(new long);


And it is entirely incompatible with these definitions

//list functions here
long ForceInPounds(long);
long FindMax(long);
long FindAvg(long);


With the result that you pass a pointer to a long (ie, its address in memory), to a function which is instead expecting the value of a long.

However, it's going to be hard to propose a solution until you edit the body of the functions into your question.

There's probably no reason to use new here at all - let the functions allocate their own temporary variables on the stack, since they seem to return a value rather than a pointer.  Most likely even if this worked, the new long you create would be abandoned - ie, a memory leak.