Need Help identifying an overflow or builtin filter

[djkdawg]

i bought this tank from a women who knew nothing about, i put a pump flow filter inside the box to blow the water back out and it seems like its working fine that way, but i seen another tank with an overflow on it and it was attached to a sump, does mine work as an overflow and attach to a sump, am i missing pieces ? sorry for the video being sideways, i am also not sure what size the take is.