Do I need a sub-panel near my hot tub?
Normally wiring like this could go into a GFCI disconnect and directly into a prewired hot tub. If you purchased individual parts, then you would go to a sub panel adding separate GFCI breakers for the heater and motor, etc..
Unfortunately the wiring provided is only good for 240 Volt,30 Amps. Two 30 Amp breakers do not equal a 60 Amp service.  It will not handle a hot tub the needs 50 Amps. You might be able to get a hot tub that only requires a 30 Amp circuit. If you do get a hot tub that requires a 50 Amp service, then you'll have to get larger wire run from your main panel to the hot tub and get a 50 Amp breaker.