Goto suntour’s site then under the service tab find you fork’s manual.
http://www.srsuntour-cycling.com
I randomly checked one fork and they don’t provide an oil type or volume. At 50 and 100 hours of use they recommend factory service.
Most people change the oil annually and replace seals at the first sign of leakage. I don’t do my own fork maintenance anymore, I just send it to someone for a full dose of loving every year.