Farmed Salmon just like Wild Salmon does contain a bit of mercury bu the mercury that Salmon even Farmed Salmon contains is a small amount and nothing to be worried about.
Just avoid eating too much of the Salmon to prevent getting mercury poisoning even though you're very unlikely to be able to eat enough Salmon to get mercury poisoning it's still best to be cautious and avoid eating too much of the Salmon.
If you think you might have mercury poisoning or have eaten too much Salmon and gotten too much mercury then a doctors visit would be a good idea.