My 2006 Mazda 3 with manual transmission does not have a transmission dipstick. How can i check the fluid level? and thus how can I refill it? I have checked the manual and there is no mention of where to check for it nor how to refill it. It only mentions the kind of fluid to replace it with. I also searched online for information but I can't seem to find anything that has a straight forward or clear answer.
Virtually no cars with manual transmissions have transmission dipsticks, because the only practical option is to drain and replace the fluid, not to top it up, and you wouldn't normally even think about changing the fluid until 100,000 or 150,000 miles.
Transmission oil is usually much thicker than engine oil - for example 75W85 or 80W90 grade, not 0W20 or 5W30. Unlike engine oil it doesn't get burnt when the engine is running, so unless there is a visible leak the level will never change. Unlike auto transmission fluid, it doesn't get hot either - in a manual transmission the heat when the transmission is "slipping" is generated in the clutch, not in the gearbox.
If you really want to check the level, take the filler plug out and look inside, but unless there are symptoms that something is actually wrong with the transmission, doing that is a waste of time.
To change the fluid, there will be a drain plug and a filler plug on the gearbox somewhere. Often, the best (or only) way to refill with fluid is to use some sort of pump device attached to the fluid bottle - there is no way to just pour it in, as you do with engine oil.