Translation:She thinks that store's clothes are not very good quality.
I think it's acceptable. Don't forget that English is spoken in many different regions, so different regions will have different ways of expressing things. The main thing is that the sentence is grammatically correct.
I translated "She thinks that the store's clothes quality is not that good." Which took me a long time to construct, even though I am native. I also think it is perhaps not technically grammatically correct, because there should be an apostrophe after "clothes". I do agree that perhaps other alternative translations should be offered, such as "The quality of the clothes in that store isn't good." or "The clothes in that store aren't of good quality."
it is unnatural. there should be a way of opting out of being forced to translate sentences like these. there are dozens of ways to express this idea, and the one that is accepted doesn't sound like a native speaker. I have resorted to copying and pasting these from notepad rather than having to think about it any more.
My answer of "She thinks that store's clothes quality are not very good" is apparently wrong.... there is no suitable options to provide a clear English sentence! ie "She thinks the clothes from that store are not good quality" would be much more suitable. Duo fix this!