You always can use a microflow to parse this string and cut it up. I would start searching for the : in the string and from there find the first space before the : You can then compare that string to a standard list Firstname, Middle name etc. to see which field this string part needs to go. Then retrieve the next : and field so you can retrieve with substrings the part between the first field and the second field because that is the value you need to store in field 1. If no : can be found anymore then the last part of the string can be stored in the last field.
It might sound a bit complicated but with microflows you can do a lot of complicated string manipulations.