If you are thinking on hardware sizing and planning migration, and you want to find how comparable are CPU resources on an Azure SQL VM (IaaS) compared to CPU resources on an Azure SQL Managed Instance, sure you can find some guidelines and information on this support article.
But, if you want to find how comparable are CPU resources on an Azure SQL Database (PaaS) compared to CPU resources on an Azure SQL Managed Instance, then they may not be directly comparable, because they have different underlying architectures and resource allocation mechanisms. You may have to run the same workload on both environments and compare how many CPUs you may need to get the expected/target performance you need.