MBOX file contains the simple plain text in the file and it is generated by the thunderbird email client. It also supports multiple email clients. Oth the other hand, Gmail is the most used email service. Every individual and most professtional use Gmail services. Its service quality is high and provides more features as compared to the MBOX format. If you want to migrate your file from MBOX to your Gmail account. Then you can read the information contained through this blog that is Import MBOX to Gmail Account.
With the help of MBOX to Gmail, Importer Tool allows users to import unlimited MBOX files. It successfully exports MBOX to Gmail and imports MBOX to Gmail with text, attachments, folders, and subfolders, Message properties like to, from, cc, bcc, sent/received dates, and times, items, Task items, Encrypted email, and attachments.

More Info:- https://www.softakel.com/mbox/gmail/