I get "unable to find 'dc101d_us.bin' in romset 'dc' and similar messages like that on when I try to run Dreamcast command. I got all the Bios needed but I wonder if I put them incorrectly, please help.
Make sure that you've got dc.zip in the roms folder. Said archive should contain dc.dat, dc101d_us.bin and all the other BIOS files you might (or might not) need.
It is against the rules to ask where to get BIOS files, since those are copyrighter material. It is also illegal to bundle BIOS files with any amulators for the same reason. Google is your friend.
If you don't have dc.zip, create it yourself (7-Zip, WinZip, whatever Zip archiver you use) and put your BIOS files and dc.dat in there. Then put dc.zip in the roms folder.