What Office can I install on my Macbook Pro 2008 running OS X El Capitan?

Both Open Office + Libre Office are not older productivity suites, they both have current versions. I use the current version of Open Office. Libre Office is based on Open Office, they maintain their software at a faster rate than Open Office. Just check out reviews on both. I have an Early 2008iMac running El Caoitan. Open Office works well on it.

Hello,

You may be able to use an older productivity suit such as OpenOffice or Libre Office. You may also be able to use Microsoft Office or iWork for iCloud through your Mac’s web browser.

LibreOffice has really made a lot of improvements since they split from the OpenOffice project years ago. I highly recommend LibreOffice over OpenOffice. Microsoft turned off their servers to validate older versions of MS Office so you won't be able to use older versions of MS Office. If you use a third party browser such as Firefox, Google Chrome, or Vivaldi, then you can use the online version of MS Office if you have a subscription.

I'm not entirely sure, but if you want everything in a row or column to have a certain format, then you right-click (or control-click) on the row/column and select the "format" options from the pop-up menu (or find the option on one of the app's menus after selecting the row/column). There are a myriad of formatting options, so you will need to locate the numeric options.

Make sure the macOS and Office are using the same format for decimal points, dot (.) or comma (,).