So, it seems you just want to know how many from the first table is also in the second table.
You can probably run the first table through a For Each loop, then calculate the matches.
I, personally, would probably use some .net to pull in the matches. A pseudocode for this would look like this:
If Not dt1.Columns.Contains("Count")
Add Data Column "Count"
For each row In dt1
Assign count = dt2.AsEnumerable.Where(Function(r2) r2("EmpID").ToString.Trim = row("EmpID").ToString.Trim).ToArray.Count
Assign row("Count") = count.ToString
Note: this is not actual code and just showing the activity logic needed in UiPath
When calculating the count, I was comparing the values as strings, so if you need to compare them as numbers which is common, you will need a slightly different condition to convert the values to numbers first.