Change value in url than redirect with .htaccess
<p>we have a Wordpress 4.x website with some plugin that verify the availability of rooms. Now we have an url like this:</p>

<p><a href="http://www.pluto.com/en/check-availability/?lang=en&amp;param1=val1&amp;param2=value2&amp;param3=value3&amp;" rel="nofollow">http://www.pluto.com/en/check-availability/?lang=en&amp;param1=val1&amp;param2=value2&amp;param3=value3&amp;</a><strong>param4=838</strong>&amp;param5=value5&amp;param6=value6</p>

<p>We want to change param4=838 with <strong>param4=631</strong> than redirect to the new page:</p>

<p><a href="http://www.pluto.com/en/check-availability/?lang=en&amp;param1=val1&amp;param2=value2&amp;param3=value3&amp;" rel="nofollow">http://www.pluto.com/en/check-availability/?lang=en&amp;param1=val1&amp;param2=value2&amp;param3=value3&amp;</a><strong>param4=631</strong>&amp;param5=value5&amp;param6=value6</p>

<p>We want to do this with .htaccess. How can we do that?</p>