If modifying a pattern how does one know if you should use a larger crochet hook or a

I'm crocheting a round rug using a rope and you crochet Loosely around the Rope so the pattern calls for 1/4 inch colored rope with a 5 mm crochet hook but I couldn't find any 1/4 inch rope I found smaller rope which is 5/16 and if I use the five millimeter crochet hook none of the Rope shows up in the pattern and it's supposed to so should I use a larger crochet hook or a smaller crochet hook do you know what to do for 4 ply yarn and it's 5/16 thickness colored rope because I couldn't find 1/4 inch rope

I've never attempted such a project but I think maybe a smaller hook will produce spaces that allow the role to show through. I'm sure you've tried many different books but maybe also try relaxing g of tightening your tension as well. I hope you can find a solution