this assumes that your phone number is in L2.
add a new column in M, paste the first formula in M2 and then copy it down the column.
copy the column and paste just the values into L2.
then empty column M and paste the second formula in M2 then copy it down the column and copy the column and paste just the values into L2.
finally, copy the third formula into M2, and also copy it down the column and copy the column and paste just the values into L2.
now L2 will have properly formatted 10 digit phone numbers.
this will not help you with entries that have more than the 10 digits. you can do those manually, or create more complex formulas.