Norway uses the Norwegian Krone (NOK). There are no legal restrictions on the amount of cash you can carry within Norway or bring into/out of the country.
However, customs regulations apply for large sums. If you carry cash or monetary instruments valued at 25,000 NOK or more (or foreign currency equivalent) when entering or leaving Norway, you must declare it to Norwegian Customs. Failure to declare can result in fines or seizure.
For safety, consider using cards or electronic transfers for large amounts.