Change the Renew link of the PMPro My Account Page to a button using CSS.

renew-link-button-change.css

/* 
*
* The following CSS code will alter the "Renew" link of your Paid Memberships Pro Account page and make it into a button. If you do not have an expiration date set for your membership level and thus no "Renew" link, the first link will be affected by the CSS. In most cases, this will then be the "Change" membership link.
* Add this CSS to your WordPress Customizer's Additional CSS section (WP Dashboard > Appearance > Customizer > Additional CSS)
* Code Recipe written by Paul Barthmaier - https://gist.github.com/pbrocks
*
*/


#pmpro_account-membership > table > tbody > tr > 
td.pmpro_account-membership-levelname > div > a:nth-child(1) {
	border: 1px solid bisque;
	padding: .3rem 1rem;
	background: rgba( 250, 128, 114, 1 );
	text-decoration: none;
	color: rgba( 255,255,255,.9 );
	-moz-box-shadow:    1px 1px 2px 2px #ccc;
	-webkit-box-shadow: 1px 1px 2px 2px #ccc;
	box-shadow:         1px 1px 2px 2px #ccc;
    -webkit-transition: all .4s;
    transition: all .4s;
	margin-right: 1rem;
}

#pmpro_account-membership > table > tbody > tr > 
td.pmpro_account-membership-levelname > div > a:nth-child(1):hover {
	color: rgb(0,243,143);
	background: rgba( 250, 128, 114, .5 );
	-moz-box-shadow:    1px 1px 2px 2px #999;
	-webkit-box-shadow: 1px 1px 2px 2px #999;
	box-shadow:         1px 1px 2px 2px #999;
}