How to Reorganize Microsoft Access Table
I think your best bet is to do the restructuring in Access. After you're confident everything works, you can 


create tables and constraints in PostgreSQL,
export tables from Access as CSV files, and 
load the CSV files into PostgreSQL.


Everything works includes application code.

Make sure your Access database is backed up, copied, and not in use before you make structural changes. 

To restructure tables in Access, 


select distinct rows into a new table ("make table" query), or
create views (saved queries) that select the right rows and columns, or
copy a table, open it in design view, and delete irrelevant columns. (You'll probably want to delete some columns from the original table, too.)


I'm pretty sure Access lets you export the results of a query, so you can build queries that have the right structure, then export the queries.