Fetch Client Portal ID to display Client Name

Fetch Client Portal ID to display Client Name

I am trying to somehow fetch client name based on customer portal ID.

So.......

I have a form " TMP_Order_Form" which contains a field called " Client_Name" and " Client_ID"



I have another form called " Clients" which contains fields " Company_Name" and " Client_User_ID"

So I am hoping when loading form "TMP_Order_Form" it will see who the customer log in ID is then pull the data from here and populate the field "Client Name" in my order form




I have tried fetching the data but I seem to get bigint and String errors.

Can someone please give me some help, Im really stuck :( Is there an easy solution please?

Because of the errors I tried the below without any luck

Fetch_Client_Name  =  Clients  [ID == input.ID];
input.Client_Name = Fetch_Client_Name.Company_Name;

Thanks in advance
Stefan