You just need to find a suitable source for 1300mg of Omega 3 fatty acids. Most fish oil pills will advertise boldly how much fish oil they have. You have to look close to find the amount of EPA and DHA. With typical fish oil pills, you need 5 a day to get 1300mg. If you want to use a different source of Omega 3 (algal oil, krill oil, etc.), look closely at the label and do the math.
Do you even need fish oil if you’re using heavy cream? There should be about 1900mg of omega 3, and a 3:2 omega 6-to-3 ratio.
looking at https://ndb.nal.usda.gov/ndb/foods/show/299329 in 100g of heavy cream there are 9mg of EPA and 0mg of DHA which are the two you need.