What are the possible combinations of a 4-digit number with the numbers 0-9?

I have this thing on my phone so that I can like unlock it, but I forgot my code, so I need the possible combinations of a four digit number with the numbers 0-9.What are the possible combinations of a 4-digit number with the numbers 0-9?
There are 10,000 combinations.





0000


0001


...


9998


9999





If you can try a code every 2 seconds, it'll only take you about 5 and a half hours to try them all, though the expected time it would take is 2 and a quarter hours.





If you can only use each number once (which seems unlikely), then there are 5040 combinations.What are the possible combinations of a 4-digit number with the numbers 0-9?
10*10*10*10 this is assuming you can have repeats