Magnification Alteration = extension/focal length

so a 50mm extension tube could give you an maximum magnification of 50/28 ~ 1.6X (if the lens does not get in the way). Given that there’s no extra glass, the picture will be as good as the original lens can do. You’ll probably lose all automatic aspects of your lens/camera system with a low price set of tubes.

A 2X TC will give a enlargement of double what you can get without it; likely something like 1/2X.

A good solution for your situation is a Raynox DCR 150 ($50) that clips onto the front of your 28-300 zoom and will give a big, continuous variety of magnifications (about 2X max) at a sound working distance (about 8″) at the same time as preserving all the automatic features of the lens/camera. As well as it is simple to hold & click on & off.

You should also be familiar with extension tubes dont really magnify, but instead alter the range at which you can focus. So with a 50mm a focusing like 5cm to 10cm but this all relies upon on the size of the tube and the lens. There a great way to begin close up photography but you’ll like a prime lens which you can manually change the fstop or you’ll get annoyed fairly rapidly

Teleconverters and extension tubes have 2 different reasons. A converter has glass and “has an extension of” the focal length of you lens so your zoom lens would be a 56-600 with a 2x converter. In addition, with a 2x converter, you lose 2 stops of fstop in effect. A 1.4x acts to be the same, just multiply the focal length by 1.4.
Extension tubes shift the photographic lens away from the camera sensor and enable you to focus very close. They are just hollow tubes. They generally come in a collection of three. They allow you to turn your lens into a “close up” of sorts.