I am not sure what you want assess: the quality of the studies being reviewed, or the approach to the literature review itself. Either way, a search on Google Scholar would be productive
A good start is to check out AMSTAR proposed by Shea et al. (2009). Here is the full citation.
Shea, B. J., Hamel, C., Wells, G. A., Bouter, L. M., Kristjansson, E., Grimshaw, J., Henry, D. A., & Boers, M. (2009). AMSTAR is a reliable and valid measurement tool to assess the methodological quality of systematic reviews. Journal of Clinical Epidemiology, 62(10), 1013–1020. https://doi.org/10.1016/j.jclinepi.2008.10.009
Hello, Ayesha Yasin for mix-methods studies you will have to assess both quantitative and qualitative parts of each mix-methods study. I suggest you check Joanna Briggs Institute Manual for conducting a mix-methods systematic review, chapter 8. The link for the manual is below: