NNT calculation should be relatively straightforward but it may be more complicated to get the standard error for meta-analysis.

The website has provided some essential formula for doing the calculation:

https://www2.ccrb.cuhk.edu.hk/stat/confidence%20interval/CI%20for%20ratio.htm#example

This link, http://fmwww.bc.edu/RePEc/bocode/m/meta_dialog.html, may be useful.

Hello Fekadu, I suggest that you seek the support of epistata.org They are an independent agency for clinical research, experts in epidemiology and medical statistics. All the best

You could follow the Cochrane Handbook (https://handbook-5-1.cochrane.org/chapter_12/12_5_4_computations.htm)

All the best