The number of hops was something Andreas was talking about in a video long ago, and he argumented. I'm too lazy to look what's the exact video but it should be a video about coinjoin or mixers
I Believe this is the video you are talking about
https://www.youtube.com/watch?v=BILcJ3WtdLQ
There is no exact number of how many hops you need.
Antonopoulos says in the video that most of the coins have been in mixers in the past, and if they say they need a high number of hops they will find that most of the coins have been there.
I have been searching about how many coins have been through mixers and I found some interesting graphics.
https://www.coindesk.com/layer2/privacyweek/2022/01/25/how-popular-are-crypto-mixers-heres-what-the-data-tells-us/
The most interesting is this chart. Fresh coins are coins that have never been mixed before.
Those charts shows basically that near 70% of all mixed coins per month have never been through a mixer before.
So the number of "tainted" coins is growing day by day in a fast rate.