I'm not sure what you mean. Do you mean the 8 numbers 1-8, or the 6 numbers 1-6?
For six numbers there are in fact 720 combinations (that is, possibilities of the numbers appearing in any order). For eight numbers it is 40,320. For obvious reasons I'm not going to type them out!
Why do you need to know? What's the background to the problem?
If you want a six digit permutation of any of eight characters the total number is
8x7x6x5x4x3 = 20160
because your choice of characters is reduced every time. Given that you are not repeating any characters?
To produce a list I recommend using a spreadsheet!