It's hard to give an exact amount of fibre in one slice of dark pumpernickel rye bread as there are obviously different brands and types that would make that level vary, as well as the actual thickness of the slice (toast or sandwich for example).
On average though, you would be looking at around 6-9 grams of fibre per slice, as some have as little as 2 grams whereas other brands are noted as having 11 grams (per slice).
One thing you can do though is look on the packaging of the bread in question (that is, if you have any packaging). Most loaves of commercially made bread should include on the back the nutritional information (including level of fibre) and usually broken down per slice.
On average though, you would be looking at around 6-9 grams of fibre per slice, as some have as little as 2 grams whereas other brands are noted as having 11 grams (per slice).
One thing you can do though is look on the packaging of the bread in question (that is, if you have any packaging). Most loaves of commercially made bread should include on the back the nutritional information (including level of fibre) and usually broken down per slice.