One cubic foot is about 7.5 US gallons. Armed with this knowledge, if you had the depth of the tank, then it would become a simple matter of arithmetic.
Length x Width x Height / 231 is the equation to get gallons.
478.8 Gallon
If it's rectangular, approx. 15,840 If it's oval, approx. 12,460
To purchase a 4ft fish tank one can visit many stores or purchase them online. One can get them from The Home Depot, eBay, Walmart and All Pond Solutions.
You cannot define a volume with only two linear dimensions.
2513.45 gallons.
a tank top or skirt
A tank this size can hold a maximum of 3,590.65 US gallons of water.
3ft by 4ft
4ft 5inches = 134.62cm
At least a 1000 g if kept with other fish.best kept in an indoor pond.
In order to answer your question there is another dimension needed. width x length x depth = volume.