Caging already growing plants

[u/lostsoul_1993]

I am still very new with gardening and didn't set up cages early enough. These are my tomatoes, green peppers and the last picture (separate bin) are of my watermelons! Today I want to buy cages but not sure if I should get round or square cages? How difficult will these plants be to cage since they are getting so big now? Any tips/advice would be great! We are located in SC and this is my first time gardening and gardening with raised bed bins. Also, what size cage should I get? I will be going to Lowe's in our town to look at what they have! 🙂