What tool would you use to move Confluence to SharePoint Online?

WikiTraccs is a reasonable place to start evaluating, but I wouldn't commit before a trial with representative content. A few thousand pages is enough that finding problems after the full move could be expensive.

Pick pages with attachments, links, permissions, tables, and whatever macros you rely on. Check the resulting SharePoint pages and attachments, then ask the vendor what needs manual cleanup and how pricing works at your volume. I can't say from the information here whether it will be the cheapest or best fit.

Treat this as a redesign as well as a migration. Confluence pages and SharePoint pages don't necessarily have matching features, so no tool should be assumed to reproduce everything cleanly.

Before buying anything, agree on what has to survive: page content, attachments, permissions, links, and any other features your users depend on. Document the gaps and get management to sign off on the cleanup effort. If the scope is beyond your team's capacity, a migration consultancy may be worth pricing alongside the tool.

Consider whether all those pages need to move at all. Content owners could identify what still matters and help clean up their areas before migration. That won't replace a tool for the material you keep, but it could reduce the volume and the review work.