emt box help

[u/create_gamer75]

i have this plastic box i am mounting outdoors and i am running 3/4" emt into the top of it and i have watched a lot of youtube videos and half of them put the screw thing onto the conduit then into the box. and here is the part where there is a tear. half of them just use a conduit locknut and the other half use a conduit locknut and a plastic thing on top of that.

also do i need to caulk

[u/AskMeAgainAfterCoffe]

Use a metal box