I aim for 1.5 to 2g of DHA/EPA per day in the form of liquid fish oil, if I'm not eating actual salmon.
There are three omega-3s relevant to humans: ALA, DHA, and EPA. ALA is the omega 3 often found in plant sources. It also has not been shown to have the same health benefits as DHA and EPA. The body can convert ALA to DHA and EPA, but not very well - there is only about a 4 to 6 percent conversion rate
Focus on the EPA/DHA content in your omega 3 sources/supplements.