That's not the "cab axle number" (which would be cab to axle, usually abbreviated CA in truck specifications), because the measurement is not to the truck's cab and not to the truck's axle... but I think I understand what you're looking for: the reach from the parts of the trailer which might hit the back corners of the truck box in a turn, to the king pin of the hitch (which is generally somewhere near the truck's axle). If I have misunderstood, perhaps rephrasing the question would help.
ETI's
Escape 5.0 page includes a link to a
towing compatibility guide, but it only shows vertical dimensions, so it doesn't help with this. Some owners of the more recent tandem-axle 5.0TA/5.0 (ETI has changed the naming) have posted excellent diagrams showing additional dimensions, probably including this one... but only for the tandem-axle trailers. The original Escape fifth-wheel, the single-axle 5.0, was probably a bit shorter in this dimension.
If you instead mean the minimum distance from the truck cab to the hitch pin (which is not the same as the truck axle), ETI says something like one metre or 40" for the current model (with more restricted turning angles for shorter distances, as shown in the table on page 6 of the guide), but that would presumably be less for the single-axle because it is narrower so less clearance is needed for the trailer's front corners in a turn.