What year model Mac mini do you have...?
see > Identify your Mac mini model - Apple Support
What size and model number is your Sceptre monitor...?
If the monitor also has an HDMI input, then all you need is an HDMI cable.
If it is an old monitor that only supports VGA input, then that is the wrong adapter to use with a Mac mini.
If you have a 2010 to 2014 Mac mini, you need a Mini DisplayPort to VGA adapter.
for example: https://www.amazon.com/Apple-Adapter-Mini-Display-auf/dp/B00AVYPIJS/ref=asc_df_B00AVYPIJS?
If you have a 2018 or later Mac mini, then you need a USB-C to VGA adapter.
for example: https://www.amazon.com/Adapter-Thunderbolt-Converter-Compatible-MacBook/dp/B076X2XS9R/ref=sr_1_4?