First of all, there is not only one 297 color. There are a ton of them. You probably mean 297C.
There is not only one way to convert a Pantone color to RGB. I can summarize that there are a right way and many wrong ways.
You can not convert a color if you do not define the color space and the color profile of the output data...
You need to set up the correct values on your professional application. CorelDraw, Illustrator, Photoshop for example.
For practical reasons you can simply go to Pantone's official site https://www.pantone.com/color-finder/297-C
These conversions, (although is wrongly not stated), according to my tests use the Swop2 specification, which is for North America.
Pantone Black 70%
Again this is wrong... There are more than two dozen "blacks". You need to first define what black.
For example Black3C.
From there you do not print a flat black, you just use a percentage of the ink using some screening on the final print. Black3C 50%.
Any ink at 0% will be white, or the paper's color, meaning there is no ink.