You can try an effective tool such as Vartika Converter for OLM. This tool quickly converts all OLM file items such as emails, notes, contacts, calendars, drafts, tasks, journals, attachments, etc. Also, there is no file size limitation in this tool to easily convert large OLM file to PST with the help of this tool.
Know more info-https://www.perfectdatarecovery.com/en/store/12/vartika-olm-to-pst-converter.html