Yeah you’re right about the conversion. It’s little so you’d need a lot of ALA. It’s for sure reccomend to get DHA and EPA also.
DHA is located in your brain, and your brain has a lot of it. So thought to be extremely good for brain health. EPA good for inflammation.
Great sources are oily fish that have not been damaged too much by cooking, such a salmon/tuna sashimi, or even oily fish like sardines wrapped in foil and cooked in the oven gently. You could also supplement, my favourite would be fish oil, especially unfiltered as this is the least processed, rather than some of the super dosed products I see.