How to find specific text box/tables in ssrs

Hi All,
I am using report builder 3.0 to build ssrs reports and migrating reports from 1 environment to other. The issue here is i generally get errors like  "The Group expression for the grouping ‘table1_X’ refers to the field ‘X’. Report item expressions can only refer to fields within the current dataset scope or, if inside an aggregate, the specified dataset scope. Letters in the names of fields must use the correct case."
Generally I know where is it pointing to but in this case I am not able to find it. Please help.
Regards,
P M-S