According to the study of millennial and Gen Z adults aged between 18 and 39, almost half (48%) could not name a single concentration camp or ghetto established during the second world war.

Not surprising as it was close to 80 years ago.
How many adults can name a single POW camp during vietnam or a single campaign offensive during the Korean war without looking it up online or in a reference book?
I bet you it would be less than half.

Almost a quarter of respondents (23%) said they believed the Holocaust was a myth, or had been exaggerated, or they weren’t sure

That's a lot of different answers to lump together. The first is egregious; it's not a myth. The second is plausible: it's possible it's been exagerated not due to malfisence or politics but merely shoddy records or liberal estimates. The third is reasonable; if they don't know or aren't sure what the numbers are, it's good to admit that.

Eleven per cent of respondents across the US believed that Jews had caused the Holocaust, with the proportion in New York state at 19%, followed by 16% in Louisiana, Tennessee and Montana, and 15% in Arizona, Connecticut, Georgia, Nevada and New Mexico.

This is interesting. If you look at the map on the actual survey [1], you'll note it's very spread out with no (seeming) rhyme or reason for why NY is 19% and montana 17% but IL and IA are 8% and 6% respectively. Very odd.

[1] [claimscon.org]