Is this outside service panel a wet location? What cable type to use?
NEMA 3R (outdoor) does not normally have gaskets, it just has a drip pattern that channels water away from live components, and wire is required that is wet location rated. The labeling on the reverse of the cover of the cabinet should indicate the NEMA rating.
The term &quot;Cable&quot; normally describes a multiconductor assembly, which isn't really appropriate for a new wet location in-use receptacle. There are limitations included in the installation documents that tell you where penetrations are allowed in the cabinet that keep the 3R rating. Probably easiest to use a short piece of 1/2&quot; PVC to a weathertight junction box and use THWN conductors. The W is wet location. All THHN conductors I have ever seen are dual rated THHN/THWN, but keep your eyes open, there might be an exception.