..You may have to see what the hardware specs are for that Mac..
Then you could learn which later macOS it could use to upgrade.
If the MacBook Pro is newer, it may be able to handle a more recent OS.
From the little you've stated here, your older Mac may need first be up-
graded to El Capitan 10.11.6 from Mavericks 10.9.5. ~ Not all that can run
10.9.5 would go as far to run Catalina 10.15.6; hardware is a limiting factor.
Mac compatibility with newer macOS/OS X is hardware dependent so you know.
• How to upgrade to OS X El Capitan 10.11.6 - Apple Support
https://support.apple.com/en-us/HT206886
• How to upgrade to macOS High Sierra 10.13.6 - Apple Support
https://support.apple.com/en-us/HT208969
• How to upgrade to macOS Mojave 10.14.6 - Apple Support
https://support.apple.com/en-us/HT210190
Each of these generally suggest hardware model suitability; most
Macs would require hardware upgrade to run later macOS system.
Be sure you've backed up your computer's hard drive; the backups
may include more than Time Machine (on external HDD) such as a
boot-capable 'full system' Clone; or another incremental archive.
• How to reinstall macOS from macOS Recovery - Apple Support
https://support.apple.com/en-us/HT204904
• How to erase a disk for Mac - Apple Support
https://support.apple.com/en-us/HT208496
For some ideas on hardware upgrades for most Macs see:
https://eshop.macsales.com/upgrades/
Examples of quality DIY replacement batteries for Mac portables
can found by Mac model and detailed by specs on this page:
owc Battery Replacement Kits for MacBook Pro/MacBook Air/ & MacBook
also note owc [..DIY Install Videos..]
Take care & good luck!🌞🎣