try there but as rule of thumb
matx most common in compact branded systems, tend to have only 4 expansion slots on the case/mobo, motherbaord is compact nearly square
atx board als very common tends to have 6 or 7 exapansion slots on case/mobo
motherboards reactangular large9nearly square if lots of coolers etc onboard)
older dells and some others have BTX format, micro or full size hard to replace
mini itx is quite rare and very compact
get a model numbr of the board or system and check its sepcs online