Dear Deepak Suthar

You can get relative values of thin film thickness using UV-Vis spectrophotometer. What I meant is that you need to have meaurrd values using a surface profiler for a material, which you make diffetent film thickness. Then measure the transmission of all films including one film with known thickness, so you can work out the unknown film thickness based on the transmission at a specific wavelength. Such technique only give you relative values of your film thickness. If your films are much thicket than micron meter range, you could use a different technique of optical inference fringes to work out the film thickness by knowing the refractive index of a material.

If you see interference fringes you can use those. Most rigorous way is to fit data if you know refractive index, e.g. using OPTICAL https://www.bo.imm.cnr.it/users/centurioni/optical.html. Link has a paper and its references will take you to more direct ways to calculate thickness from fringe spacing.

If it is a uniform film, just use the Beer-Lambet law, can not be more simple