This has been asked and discussed here repeatedly. While you need the best scope you can afford, there is no magic threshold for "seeing ___cal. bullet holes at___". It is highly dependent on light and contrast.
The best suggestion so far is to use Shoot-N-C targets. Although a bit pricey, you can paste the heck out of them with repair dots and make them last a long time. You can buy a lot of Shoot-N-Cs for the additional cost of a better scope.
I make many of my own targets using white poster board from Walmart. You can stick pasters on it, or as I do get target stamps and an ink pad. I got mine from Sinclair years ago. On our range at 200 yards , I can see .223 bullet holes in the white board with my rifle scope
Most commercial targets are too cluttered, made for visual appeal to the customer, like fishing lures.
To add a perspective, I shoot competition with a .22 at 200 yards in two different events on two ranges, one facing north and the other south, red or black bulls. I can't reliably spot bullet holes in the bull even with a 20-60 Zeiss. Depends on light conditions. Did I mention mirage?
Paul
That is some good advice there. A $1.50 poster board from Walmart and a marker will get you a lot of target that is pretty easy to spot holes in, regardless of distance.
