I would avoid getting into a situation where you have either text or a numeric value in a text field in the first place. Rethink your fields and calculations. Ambiguous data (text/numbers) should be cleaned up at the point of key entry or importing.
You probably could do a simple formula knowing that a number in a business setting consists of a {set of digits} possibly proceeded by a plus or minus sign and at most one decimal point amid the digits but it is just an exercise if difficulty.
QuickBase does not use scientific notation for numbers but technically you could have this in your string and ToNumber () will convert it correctly.
ToNumber("34e5") => 3400000
Or you could use JavaScript where any manner of parsing and data conversion is possible. Anyone here that could write a formula to accomplish the task you ask about could do it easier in JavaScript. Replace the formula language with JavaScript is my advice.
It strikes me as extremely odd that for a no code platform the first thing you have to do is master the formula language and all its quirks. _\_(_)_/__
