@Ellen,
If your cross bars are factory bars you should be good to go. The connection system on the Thule Snowpack is about as universal as it gets (I have a SUP Taxi with the same system and it connects to all my different racks). Without knowing the year of your 4Runner and whether the rack is factory or after market I can't speak with 100% confidence. It is always advisable to have an expert at your local store take a look (and you can schedule someone to install it for you if you like!) to double check for you. I hope this helps, thanks!
John
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