Mixed use refers to one structure, not multiple structures. Your property has multiple dwellings, a multi-family and a 1-4. This loan will be reported as a purchase.
Look to page D-5 in the GIR for purchases of mixed-use property.
Since you are dealing with multiple properties you will also want to scan the GIR for multiple properties.
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The opinions expressed are mine and they are not to be taken as legal advice.