How do I access table field type value?
You can grab the content of a field for an element with

$myTableField = $entry-&gt;getContent()-&gt;getAttribute('fieldHandle');


You can modify the variable and send it back with 

$entry-&gt;getContent()-&gt;setAttribute('fieldHandle', $myTableField);


Since you are probably in an event you should make sure your entry has the correct type and the correct section

$entry-&gt;getSection()-&gt;handle === 'mySectionHandle' &amp;&amp; $entry-&gt;getType()-&gt;handle === 'typeHandle'


If you want to change every table field and not just a certain one you can do

foreach($entry-&gt;getFieldLayout()-&gt;getFields() as $field){
    if($field::class === 'insert the class of the field here'){
        $table = $entry-&gt;getContent()-&gt;getAttribute($field-&gt;handle);
   } 
}