Inspect the XML file with a regular editor such as Notepad++ or Sublime Text.
The line number in the JMeter error message marks the line in the JMX where the problem is to be found.
A common error is the use of an ampersand (&) within the name of a JMeter component. The ampersand has special meaning in XML as described in https://www.techrepublic.com/article/beware-of-the-ampersand-when-using-xml/
and needs to be avoided or escaped