We have found one software suitable in our database for this conversion.
It looks like that you can import .olm files to the Mac version of Microsoft Outlook and with that app you can also export the contacts and save them to one of the supported formats - including VCF format.
Except for that, you might have luck with some dedicated Outlook converters, but these are usually somewhat expensive. Of course, if you do not have access to Mac or do not have any friends that have, such programs are likely your only option for olm to vcf conversion.
Mac version of the popular e-mail client and personal information manager from Microsoft
OLM
Files with olm extension can be quite often found as email client databases from Microsoft Outlook for Mac. Similar to PST format in purpose
VCF
Files with vcf extension are almost always contacts saved in vCard format. Typically used various Personal Information Managers or e-mail clients (for example Outlook), as well as exported from mobile phones, for the purposes of sharing or migrating contacts from one device to another.