What is 510x10^6km^2 in ft? pls show in dimensional analysis fashion?

so I had
(510x10^6km^2)(1000m^2)/1km^2(100cm^2)/1... and this is where I get stuck cus I still end up with square feet and its not supposed to end in square feet. should I just take the square root of km^2 like my friend told me...? pls help
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