To include the product category thumbnail (125 × 125 px) in your product category items (buttons), use the following:
$product_cats = get_terms([
'taxonomy' => 'product_cat',
'hide_empty' => true,
'parent' => 0,
]);
foreach ( $product_cats as $key => $parent_term ) {
$thumb_id = get_woocommerce_term_meta( $parent_term->term_id, 'thumbnail_id', true );
$size="thumbnail";
$image = wp_get_attachment_image_src($thumb_id, $size);
printf( '<button class="tablinks %s" onclick="https://wordpress.stackexchange.com/questions/337144/%s"><img src="https://wordpress.stackexchange.com/questions/337144/%s" width="150" height="150" />%s</button>',
$key === 0 ? esc_attr( 'active' ) : '',
"myFunction(event,'{$parent_term->name}')",
$thumb_id ? $image[0] : wc_placeholder_img_src($size),
$parent_term->name
);
}