I need to make a correlation with satellite setienl 5p TROPOMI values vs. in situ, and I need comparable values to be able to graph and make a correlation

how to convert values of the (VCD) mol / m2 SENTINEL 5P to comparable values on the surface as mg / m3, ppm or ppb. What should I take into account for this conversion or how should I make a TROPOMI vs. on-site correlation? Thanks