To my understanding the STROBE checklist was developed to guide the reporting observational studies instead of a risk of bias assessment tool such as Cochrane's ROBINS-I.
Mam u can use MINORS criteria(https://onlinelibrary.wiley.com/doi/full/10.1111/jep.12889) and its feasible to use. Or the new ROBINS-1 by Stearns et.al. criteria(https://www.bmj.com/content/355/bmj.i4919)
ROBINS-I is the way to go. In particular, Chapter 25.5 of the Cochrane Handbook for Systematic Reviews of Interventions specifically deals with how to use the ROBINS-I for uncontrolled studies and contains very helpful information about how to adapt it for single-group studies. Needless to say, some risk categories will be de facto high-risk, as correcting for confounders becomes incredibly difficult in these kinds of studies.
Link for the Chapter: https://training.cochrane.org/handbook/current/chapter-25
This may be an extremely late answer, but I believe may be of help for future reference. Also for future reference, it is incorrect to use the STROBE tool as outlined in: da Costa BR. Uses and misuses of the STROBE statement: bibliographic study BMJ Open 2011;1:e000048. doi: 10.1136/bmjopen-2010-000048 (link: https://bmjopen.bmj.com/content/1/1/e000048)