Transfer 500 articles to Wordpress

We are moving our website to Wordpress from a custom system and have about 500 posts that we need to move over. The old system does not have a way to export the data, so this may need to be done manually. Project requirements are below:

1. Move 500 records from old system to Wordpress
2. In Wordpress there is a custom post type called 'Articles.' All items will be created here as new 'Articles'
3. In the old system, data can be copied from the admin area, but the downloaded file will need to be retrieved from the front end.
4. Here is the data in the old system: https://tinyl.io/4mdA
5. Here is the data in the new Wordpress system: https://tinyl.io/4mdC
6. Attached are examples of what the pages look like in each system
6. Fields to transfer:
WP / Old system
>Title: copy from 'Headline'
>Publish Date: Publish Date
>Show this item: Show this item
>Full Issue: If Headline in old system is "Full Issue" then check this
>Authors: Authors
>Pub Year: Pub Year
>Citation: Citation
>Short Description: Short Description
>Link to: Link to
>Categories: Select 'The Journal of Reading Recovery', 'Journal Archives' and create a new child category for the season and year. For example, if published in December 2019, create a child category called "Winter 2019" under "The Journal of Reading Recovery" and assign to that. The new system uses this child category to organize the articles on the front-end.
* below fields are dependent on the 'Link to' field. Each article only has one.
>Article Link: Click 'Continue' and copy the URL from old system
>Enter News Story: Click 'Continue' and copy the text from the old system
>Open a File: Need to download the file from the front-end. The old system doesn't seem to have a way to download it from the admin section

Please let me know if you have questions.