Extract the values from multi-select custom field and and change them

[odmin]

Hello!

I will be very grateful if someone helps to solve the following problem.
I have a customfield with the multi-select type, often it has several values, i.e. if you extract the data, the output is approximately as follows:

I need to write a script that would extract values from this field, and with each value would do the following:
- I would add some text to the value and then write it to another text field.
Each value processed in this way from the multi-select customfield should be added to the end of the text field.
I know how to extract data and work with it from a regular customfild, but I don't know how to do it with multiselect customfield.