Is maximum focal length of P1000 similar to 300mm kit lens provided with APS-C cameras? Either in terms of 35mm or 1/2.3(sensor size found in P1000) format.
No they are not similar. They are not even close.
The Nikon P1000 has an actual focal length of 4.3-539mm and a crop factor of 5.56 which yields a 24-3000mm equivalent focal length.
A Nikon APS-C camera with a 300mm lens has a crop factor of 1.5 which yields a 450mm equivalent focal length.