i want to select a part of the cell content from a table read from a txt/csv file, for eg, if i have a column Value

i) In this case, i want to keep the last two items always, no matter the length of the cell content, so my answer willbe

ii) and i want to associate that with another table (read from a txt file)

saying if 'Value' column has '4d' pick 'z3' and if 2a then pick 'x1'

I tried using substring and string length for the first part but i think i am missing subsequent steps. Please help. Thanks.