ToneBooster’s Broadcast plugin is a multi-band compressor & limiter.
It will enable you to achieve store-bought loudness.
There are 2 free versions of Broadcast which work in Audacity on Windows …
v2 … https://web.archive.org/web/20130329211641/www.jeroenbreebaart.com/audio_vst_jb.htm (32-bit)
v3 … https://forum.audacityteam.org/t/free-v3-toneboosters-plugins/64538/3 (64-bit)