Create a lsrt day month from an text

I all, I new in Knime, and I want to create a date from a text like this: “20201205” but in a date of last day of this data as: “31-12-2020” or at first day of month like: “01-12-2020”.

I need do this at many columns that originaly are text, and I know that this is possible using “java snipped” but Im not an Java advance programer. And I know that this is posible using “String to date” and using some extra node, but my data is really big and I really want to reduce the number of steps/node to use to reduce the time and memory use…

I really appreciate your help.

Thanks.