There is no correct number. Link where a reader would genuinely benefit from the destination, and ensure every important page receives links from several others. Counting links is a proxy for a judgement that should be made per link.
Descriptive anchor text matters more than volume — 'AI visibility measurement' beats 'click here'.
A page receiving no internal links will underperform regardless of its quality.
Links inserted purely for SEO read as such and reduce trust.