Help needed to create an install usb or dvd.

I am under the impression that by sending you an email it gets posted on your linux users group...

I've been trying to create an ubuntu install disc for my older mac book pro (running Mavericks) and have spent many hours searching online for how to do it. Nothing has worked!  Here are a few of the terminal codes and the error messages that I get: I even used Unetbootin which creates the usb but the mac won't mount it!

 

hdiutil convert -format UDRW -o ~/Desktop/ ubuntu-16.04.3-desktop-amd64.img ~/Downloads/ ubuntu-16.04.3-desktop-amd64.iso

hdiutil convert ubuntu-16.04.3-desktop-amd64.iso -format UDRW -o ubuntu-16.04.3-desktop-amd64.img

 

hdiutil convert ubuntu-16.04.3-desktop-amd64.iso -format UDRW -o ubuntu-16.04.3-desktop-amd64.img       image not recognized

 

ubuntu-16.04.3-desktop-amd64.iso

 

PowerMacs-MacBook-Pro-6:~ powermac$ hdiutil convert ubuntu-16.04.3-desktop-amd64.iso -format UDRW -o ubuntu-16.04.3-desktop-amd64.img

hdiutil: convert failed - No such file or director

 

PowerMacs-MacBook-Pro-6:~ powermac$ hdiutil convert -format UDRW -o /Users/Powermac/Desktop/ ubuntu-16.04.3-desktop-amd64.img /Users/Powermac/Desktop/ ubuntu-16.04.3-desktop-amd64.iso

hdiutil: convert: only a single input file can be specified

 

PowerMacs-MacBook-Pro-6:~ powermac$ hdiutil convert -format UDRW -o ~/Desktop/ ubuntu-16.04.3-desktop-amd64.img ~/Downloads/ ubuntu-16.04.3-desktop-amd64.iso

hdiutil: convert: only a single input file can be specified

 

PowerMacs-MacBook-Pro-6:~ powermac$ hdiutil convert ubuntu-16.04.3-desktop-amd64.iso -format UDRW -o ubuntu-16.04.3-desktop-amd64.img

hdiutil: convert failed - No such file or directory

 

PowerMacs-MacBook-Pro-6:~ powermac$ hdiutil convert -format UDRW -o /Users/Desktop/ ubuntu-16.04.3-desktop-amd64.img /Users/ Desktop/ ubuntu-16.04.3-desktop-amd64.iso

hdiutil: convert: only a single input file can be specified

 

hdiutil convert ubuntu-16.04.3-desktop-amd64.iso -format UDRW -o ubuntu-16.04.3-desktop-amd64.img    hdiutil: image not recognized

 

PowerMacs-MacBook-Pro-6:Desktop powermac$ hdiutil convert -format UDRW -o /User/Desktop/ ubuntu-16.04.3-desktop-amd64.img /User/Desktop/ ubuntu-16.04.3-desktop-amd64.iso

hdiutil: convert: only a single input file can be specified

Usage:     hdiutil convert -format <format> -o <outfile> [options] <image>

Can anyone tell me how to create an install usb or DVD for mac, pretty please. Thanks Charles