The RegEx extractor is not a “standard” KNIME node. You need to install the extension Palladian for KNIME from the an update site. See the link. And add the link to your KNIME - File - Preferences - Install/Update / Available Software sites.
Also, you could do it with some steps more (create variables, make some calcs for each value, create a chunk loop to validate row-by-row and make some calc to sum each value to a total variable… more work to do, but you’ll have the same result.
Looking row by row with chunk loop, then, split number by number using substring function and variables to change the position and save as a row result until the loop end and then, using a groupby node to sum all results… more complex, but it works.