If you have the design already you'd want a dev, not a designer, unless you want them to improve on it.
I know you've said you're busy, but for the amount of time you'd potentially be involved with another person, and going through it, you could drop the design into GPT and ask it to walk you through what to do. Shopify has it's own templating language so it'll likely give you stuff you can copy and paste, probably where to drop everything too.
I think it's sensible to assume you'll be paying someone. If you don't want to have a go, I'd set a budget and see who bites. Not sure if that's allowed in here, but good to have that in mind, then have a look around for people that fit that budget.
