Do help us out with the name of which terminal application you're using.
Part I: Increasing the Font size of your Terminal window (if its GNOME):
Here's how you can do it:
Open your terminal window [Shortcut: Ctrl
+ Alt
+ T
]
Click the hamburger option in the top right corner of the terminal window >> Click on Preferences option
OR
Right-Click anywhere within the terminal window >> Choose Preferences option from the context sensitive menu
On the preferences window, go to "Text" tab
Click “custom font” check box to enable the font customization and alter the Font style and Font size
Click on "Font-size" input field >> Pick your font style and move the slider (at the bottom) to determine your ideal font size
Click on "Select" to ensure your chosen font style & size get implemented.
Close the preferences window and save your settings.
Your terminal should now showcase the new Font style and size.
Part II: If you're talking about the generic font size
Install Gnome tool using the command: sudo apt install gnome-tweak-tool
Open Gnome tool >> Click "Fonts" tab
Configure font settings for 'Window Title', 'Interface', 'Document', and 'Monospace' through this tab.
Increase/Decrease the "Scaling Factor" to change the general Font size for your Ubuntu Desktop.
If required, remove Gnome by entering the command: $ sudo apt remove gnome-tweak-tool
Let us know how it works out for you.
Cheers,
Manu