SEO
Hi there, I'm Matt Sergej and can migrate your website hosting without losing SEO standings (24 years a webmaster, 11 years a WordPress developer, former Internet Security System Engineer at Societe Generale Group bank, covering all TCP/IP network architecture including configuring, securing and updating DNS).
You have probably post similar project, with mentioning your website is on Squarespace currently. I need to know all details before migration, including:
1. Current domain registrar and domain hosting provider.
2. Current website hosting provider.
3. Mapping of your current website URLs to your new website URLs.
And of course, all access details to change both hostings concurrently.
Yes, for keeping SEO rankings at Google it's important to allow up to 30 days to redirect old URLs to new ones (if they are changed e.g. domain and/or path e.g. subdirectory etc). In this period Google is guaranteed to update all redirected URLs to their new domain and/or path.
If your URLs won't change then it's just needed to ensure DNS changes, keeping the old hosting for max. 30 days and ensuring redirects at the old site (it's also possible to have redirects only on the new site and after migration remove them but this is less desirable in Google eyes).
I'm currently on vacation till Wednesday, Aug 29th, 8 PM CET with limited Internet connectivity here. You're welcome to ask me anything before though.
Best Regards,
Matt