merge a set of cell data to a single cell like below

aaajith_k I'd go for a Power Query solution. Connect to the table on the left and Group and Text.Combine the relevant columns. Not too difficult, but when you have never used PQ, it's not all that straight-forward to be honest. It's a bit of a learning curve to get into it.

Alternatively, I can imagine Power Pivot also achieving something similar with separate DAX measures that concatenate the Diagnosis and Service codes into a single cell.

At the moment, I'm unable to demonstrate it and upload a file, but perhaps someone else can.