This is not really a question about LibreOffice but how you use a computer or spreadsheet more generally. There are various techniques you could use. (But you do not mention your operating system, which may make a difference.) Try one of these:
o Highlight cell C2. Scroll down to row 150240. Hold down Shift while you click on cell C150240.
o Is row 150240 the last row containing any entry in column C? If so, first highlight cell C2 and then press Ctrl+Shift+down-arrow.
o Is row 150240 the last row containing any entry? If so, first highlight cell C2 and then press Ctrl+Shift+PageDown. If this causes the selection to include rows to the right of C, hold down Shift and use left-arrow to reduce the selection to a single column.
o Give your required range a name. To do this, highlight cell C2 and go to Insert | Names > | Define... . In the Name box, enter a name. The "Assigned to" box will show something like "$Sheet1.$C$2". Modify this to read "$Sheet1.$C$2:$C$150240" (without the quotation marks). Click OK. Your required range now has a name. To select the range, click the down-arrow to the right of the Name box (at the left of the Input Line) and select your new name from the drop-down menu.
I trust this helps.
Brian Barker