How many 5 digit combos in 30 numbers?

The answer will depend on how many digits there are in each of the 30 numbers. If the 30 numbers are all 6-digit numbers then the answer is NONE!

If the 30 numbers are the first 30 counting numbers then there are

126 combinations of five 1-digit numbers,

1764 combinations of three 1-digit numbers and one 2-digit number, and

1710 combinations of one 1-digit number and two 2-digit numbers.

That makes a total of 3600 5-digit combinations.