If you're trying to get consultant, the conduct procurement is the process that will facilitate it. Remember, you have to draft a contract (time and material contract) to acquire external resources. An easy way to address some of these overlap in terminologies is to know the outputs of each process. Acquire resources is primarily aimed at assigning resources unlike conduct procurement which seeks to issue a formal contract.
Process 9.3 Acquire Resources encompasses securing internal and external resources for the project whereas 12.1 Conduct Procurements specifically pertains to securing external resources (in your case consultants) by awarding contracts to sellers whom you’ve identified in your procurement management plan (12.1).
You could say that acquire resources is the overarching process while conduct procurements is more granular or more geared towards acquiring external resources through contracting.
Per section 9.3 – Acquire Resources from the PMBOK regarding acquiring resources: "The resources needed for the project can be internal or external to the project-performing organization. Internal resources are acquired (assigned) from functional or resource managers. External resources are acquired through the procurement processes."
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